When a casing within a well bore has been lost or cut loose for any reason, a connection to the upper end of the casing is attempted. This type of connection is also used in the event the casing has stuck to adjust the vertical position of the top of the casing. Such connection is referred to herein as a casing patch. It is preferred that the casing patch be made to a hanger or other suitable equipment which can be supported within a wellhead housing and that the casing be held in tension during the making of the patch.
A particularly advantageous manner of providing such casing patch is to provide a cold forging tool which is positioned within the casing and a hanger having a gripping and sealing interior contour positioned around the casing near its upper end. U.S. patent application Ser. No. 044,409, filed Apr. 30, 1987 discloses a cold forging method, apparatus and tool therefor which can be used to make a casing patch.
Casing which is in a well bore as a "fish" can be engaged internally by a device commonly referred to as a spear and when the spear has engaged, tension can be exerted on the string in which the spear is engaged to exert a tension on the casing. One disadvantage which has been encountered with the use of spears to tension casing is that considerable radial loading may be necessary on the casing and to prevent slipping of the spear, the spear slips are highly loaded. Also, the tensioning can also increase the loading of the slips against the interior of the casing. Such high slip loading has caused excessive deformation of the casing in the past.